fix(docs): use locked dependencies to install cargo-codspeed

Author: adriencaccia

crates/cargo-codspeed/README.md

@@ -31,7 +31,7 @@ cargo binstall cargo-codspeed
 ### With `cargo`
 
 ```bash
-cargo install cargo-codspeed
+cargo install cargo-codspeed --locked
 ```
 
 ## Usage